import type { Emoji } from 'masto' import type { Node } from 'ultrahtml' import { TEXT_NODE, parse, render, walkSync } from 'ultrahtml' const decoder = document.createElement('textarea') function decode(text: string) { decoder.innerHTML = text return decoder.value } /** * Parse raw HTML form Mastodon server to AST, * with interop of custom emojis and inline Markdown syntax */ export function parseMastodonHTML(html: string, customEmojis: Record = {}) { let processed = html // custom emojis .replace(/:([\w-]+?):/g, (_, name) => { const emoji = customEmojis[name] if (emoji) return `:${name}:` return `:${name}:` }) // handle code blocks .replace(/>(```|~~~)(\w*)([\s\S]+?)\1/g, (_1, _2, lang, raw) => { const code = htmlToText(raw) const classes = lang ? ` class="language-${lang}"` : '' return `>
${code}
` }) walkSync(parse(processed), (node) => { if (node.type !== TEXT_NODE) return const replacements = [ [/\*\*\*(.*?)\*\*\*/g, '$1'], [/\*\*(.*?)\*\*/g, '$1'], [/\*(.*?)\*/g, '$1'], [/~~(.*?)~~/g, '$1'], [/`([^`]+?)`/g, '$1'], [/&[^;]+;/g, (val: string) => decode(val)], ] as any for (const [re, replacement] of replacements) { for (const match of node.value.matchAll(re)) { if (node.loc) { const start = match.index! + node.loc[0].start const end = start + match[0].length + node.loc[0].start processed = processed.slice(0, start) + match[0].replace(re, replacement) + processed.slice(end) } else { processed = processed.replace(match[0], match[0].replace(re, replacement)) } } } }) return parse(processed) } export async function convertMastodonHTML(html: string, customEmojis: Record = {}) { const tree = parseMastodonHTML(html, customEmojis) return await render(tree) } export function htmlToText(html: string) { const tree = parse(html) return (tree.children as Node[]).map(n => treeToText(n)).join('').trim() } export function treeToText(input: Node): string { let pre = '' let body = '' let post = '' if (input.type === TEXT_NODE) return input.value if (input.name === 'br') return '\n' if (['p', 'pre'].includes(input.name)) pre = '\n' if (input.name === 'code') { if (input.parent?.name === 'pre') { const lang = input.attributes.class?.replace('language-', '') pre = `\`\`\`${lang || ''}\n` post = '\n```' } else { pre = '`' post = '`' } } else if (input.name === 'b' || input.name === 'strong') { pre = '**' post = '**' } else if (input.name === 'i' || input.name === 'em') { pre = '*' post = '*' } else if (input.name === 'del') { pre = '~~' post = '~~' } if ('children' in input) body = (input.children as Node[]).map(n => treeToText(n)).join('') if (input.name === 'img' && input.attributes.class?.includes('custom-emoji')) return `:${input.attributes['data-emoji-id']}:` return pre + body + post }